1. Field of the Invention
The present invention relates to selected phase change ink carrier compositions and phase change ink compositions containing those carrier compositions. In particular, the present claimed invention relates to phase change ink compositions containing a phase change ink carrier composition and at least one compatible colorant, wherein the phase change ink carrier composition contains selected polyanhydride/amine adducts.
2. Brief Description of Art
Phase change inks in digital printing applications (also sometimes called solid inks or hot melt inks) have in the past decade gained significant consumer acceptance as an alternative to more traditional printing systems such as offset printing, flexographic printing, gravure printing, or letter press printing. Phase change inks are especially desirable for the peripheral printing devices associated with computer technology, as well as being suitable for use in other printing technologies such as gravure printing applications as referenced in U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL assigned to Siegwerk Farbenfabrik Keller, Dr. Rung & Co.
In general, phase change inks are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the printing media or an intermediate transfer surface, they quickly solidify to form a predetermined pattern of solidified ink drops.
They are easy to use and safe. They can be easily loaded into the printer by the user, generally in the form of solid sticks of yellow, magenta, cyan and black ink having a consistency similar to children's crayons. Inside the printer, these inks are melted at an elevated temperature in a print head having a number of orifices, through which the melted ink will be ejected onto the desired media substrate such as paper or an overhead transparency film. Alternatively, the melted ink may be transferred to a rotating drum and then transferred to the substrate. As the ink cools on the substrate, it re-solidifies to form the predetermined image. This resolidification process, or phase change, is instantaneous and a printed, dry image is thus made upon leaving the printer, and is available immediately to the user.
These phase change inks contain no solvents or diluents that can lead to undesired emissions. In all, the use and specific design of the phase change ink addresses many of the limitations of more traditional ink and printing processes.
Furthermore, because the ink is in a cool, solid form at any time when the user can actually come in contact with the ink, and the ink is in a molten state only inside the printer (inaccessible to the user), it is generally safe to use. These inks also have long-term stability for shipping and storage.
The phase change inks generally comprise a phase change ink carrier composition, which is combined with at least one compatible phase change ink colorant. The carrier composition has been generally composed of resins, fatty acid amides and resin derived materials. Also, plasticizers, waxes, antioxidants and the like have been added to the carrier composition. Generally the resins used must be water-insoluble and the carrier composition may contain no ingredients that are volatile at the jetting temperatures employed. Also, these carrier ingredients should be chemically stable so as not to lose their chemical identity over time and/or under elevated temperature conditions.
Preferably, a colored phase change ink will be formed by combining the above described ink carrier composition with compatible colorant materials, preferably subtractive primary colorants. The subtractive primary colored phase change inks comprise four dye components, namely, cyan, magenta, yellow and black. U.S. Pat. Nos. 4,889,560 and 5,372,852 teach the preferred subtractive primary colorants employed and typically comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, C.I. Disperse Dyes, modified C.I. Acid and Direct Dyes, as well as a limited number of C.I. Basic Dyes. Also suitable as colorants are appropriate polymeric dyes, such as those described in U.S. Pat. No. 5,621,022 available from Milliken & Company as Milliken Ink Yellow 869, Milliken Ink Blue 92, Milliken Ink Red 357, Milliken Ink Yellow 1800, Milliken Ink Black 8915-67, uncut Reactint Orange X-38, uncut Reactint Blue X-17, and uncut Reactint Violet X-80, or those described in U.S. Pat. No. 5,231,135. Colored resin reaction products, as described in U.S. patent application Ser. No. 08/672,617 filed Jun. 28, 1996 U.S. Pat. No. 5,780,528 and assigned to the assignee of the present invention, are also suitable colorants.
The specific choice of ingredients, as well as their relative amounts, is of critical importance in achieving the desired application performance properties of the phase change inks. Specific physical and chemical properties sought in these inks include viscosity, surface tension, flexibility, durability, and thermal stability, as well as the ability to deliver color.
In particular, two desired properties of phase change inks are (1) durability of printed images and (2) jettability of the ink to produce images on a substrate.
The following U.S. Patents teach specific phase change ink compositions.
U.S. Pat. No. 4,889,560 teaches a phase change ink carrier composition that comprises a fatty amide-containing material which is a mixture of a tetra-amide compound and a mono-amide compound and wherein the phase change ink composition containing this carrier composition has a high degree of lightness and chroma and thin films of uniform thickness of such inks are rectilinearly light transmissive.
U.S. Pat. No. 4,889,761 teaches a method for producing a light-transmissive phase change ink printed substrate wherein a predetermined pattern of a light-transmissive phase change ink which initially transmits light in a non-rectilinear path is printed on at least one surface of a substrate; the pattern of solidified phase change ink is then reoriented to form an ink layer of substantially uniform thickness which, in turn, produces an image that will transmit light in a substantially rectilinear path.
U.S. Pat. No. 5,372,852 teaches that the selective phase change ink composition that contains a phase change carrier composition comprises a fatty amide-containing material (either a tetra-amide compound or mono-amide or mixtures thereof). This patent further teaches the preferred tetra-amide compounds are made by reacting a fatty acid, a diamine (ethylene diamine) and a dimer acid. The preferred fatty acid is stearic acid and the preferred dimer acid is a hydrogenated oleic acid dimer product known as EMPOL 1008 Dimer Acid, manufactured by the Emery Division of Henkel Corporation of Cincinnati, Ohio. The preferred mono-amides are taught to be secondary mono-amides such as behenyl behenamide and stearyl stearamide, products made under the KEMAMIDE trademark by Witco Chemical Company.
U.S. Pat. Nos. 5,750,604; 5,780,528; 5,782,966; 5,783,658; 5,827,918 and 5,830,942 all assigned to the assignee of the present patent application, disclose a number of urethane, urea and mixed urethane/urea resins appropriate for use in phase change ink compositions.
While the phase change ink compositions described by the above-noted U.S. Patents have met with great commercial success, there is always a need to improve those inks for more demanding processing conditions and different applications. Besides their performance on the printed substrates, inks and individual ink components that go into the inks also must be measured by their cost and ease of manufacturing as well as how they work in a particular printer. The ideal phase change ink for a plain paper printer is one that encompasses the best qualities from all printing technologies, such as bright, vivid color with the ability to print on plain paper or overhead transparencies and produce durable images.
Additionally, U.S. Pat. No. 5,688,312 describes a hot melt ink composition with an imide or bismide and U.S. Pat. No. 5,693,128 describes another hot melt ink composition that is the reaction product of an mono-anhydride and a mono-organoamine.
Finally, U.S. Pat. Nos. 5,176,745 and 5,310,887 teach the reaction of colorants with alkenyl succinic anhydride for use in aqueous inks.
There still remains the need for alternative hot melt or solid ink formulations that permit the tailoring of components to produce the desired range of physical and chemical properties in the resulting inks and carrier compositions for use in specific printing applications. This need is addressed in the present invention by forming reaction products with the desired range of physical and chemical properties from the reaction of polyanhydrides with amines.